Status report on species at risk in Canada. Vancouver Island Marmot Marmota vancouverensis [Rapport d'état sur les espèces à risque au Canada. Marmotte de l'île de Vancouver].

Résumé

Description: The Vancouver Island (Marmota vancouverensis, like other members of the genus, is fossorial, herbivorous and hibernates during winter. M. vancouverensis differs from other species in karyotype, skull characteristics, pelage and behaviour. It is similar to other alpine-dwelling marmots in its slow maturation, long life span, and complex social organization. M. vancouverensis persists despite a small and fragmented natural habitat base. It exhibits a « metapopulation » structure. The entire population consists of a small colonies that occasionally form and become extinct. Distribution: M. vancouverensisis endemic to Vancouver Island, British Columbia. The current population is concentrated within 5 adjacent watersheds on south-central Vancouver Island. Even within this area the population is extremely localized >65% of marmots live on 4 mountains in the central 40 km2 portion of their current range. Paleaontological and archaeological records indicate that M. vancouverensis enjoyed a broader distribution in the recent geological past. Historic records suggest that marmots disappeared from some areas quite recently (10-30 years ago). Protection: M. vancouverensis is listed as endangered under the B.C. Wildlife Act (1980). It is also listed as endangered by the Committee on the status of Endangered Wildlife in Canada, the U.S. Endangered Species Act and the International Union for the Conservation of Nature. Most colonies occur on privately owned lands. Two marmot habitats are legally protected (combined area of <400 ha). Population size and trends: The current population contains 150-200 individuals. This represents a 50-60% decline in numbers during the past 10 years. Concomitant with this has been local extinction of several colonies during this period, including some which typically contained >10 adults. Habitat: Vancouver Island marmots require three essential habitat features: 1) grasses and forbs to eat, 2) colluvial soil structure for construction of overnight and overwintering burrows, and 3) microclimatic conditions that permit summer foraging, thermoregulation, and successful hibernation. Most marmots are found between 1000 and 1400 metres in elevation, and on south to west-facing slopes. Habitat scarcity is the fundamental reason for the rartity of M. vancouverensis. Biology: M. vancouverensis is among the most social of marmots. They live in colonies which contains fewer than 5 adults on average. Females are capable of breeding at age 3, but most animals, do not breed until age 4. Young marmots disperse at age 2 or later, dispersal is fundamental to maintaining metapopulation structure. Limiting factors: The essential short-trend problem is low adult and juvenile survival. Predators and unsuccessful hibernation are the principal causes of mortality. Both factors are exacerbated by the restricted range. reproduction rates are apparently stable. There is no evidence of inbreeding depression or disease. Long -term problems probably include reduced long-distance dispersal (altered landscape connectivity caused by logging, invasion of sub-alpine meadows). The question of why marmots no longer inhabits some areas is of fundamental importance. If climatic change is principally responsible, efforts to re-establish colonies will fail and there may be little that managers can do to enhance marmot populations. Alternatively, if human-caused alteration of landscape connectivity is the problem, then reintroductions should allow recovery of the species within a reasonable time period. Special significance of the species: M. vancouverensis is one of only five endemic mammals in Canada. It is the only endemic mammal species which appears on the COSEWIC endangered list. Recommendations/Management options: Recovery Plan objectives have not been met. The current « eggs in one basket » distribution is highly dangerous. Planned recove